Mobile three-lead cardiac monitoring device and method for automated diagnostics

ABSTRACT

Methods and apparatuses, including devices and systems, for remote and detection and/or diagnosis of acute myocardial infarction (AMI). In particular, described herein are handheld devices having an electrode configuration capable of recording three orthogonal ECG lead signals in an orientation-specific manner, and transmitting these signals to a processor. The processor may be remote or local, and it may automatically or semi-automatically detect AMI, atrial fibrillation or other heart disorders based on the analyses of the deviation of the recorded 3 cardiac signals with respect to previously stored baseline recordings.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/181,330, filed Nov. 5, 2018, titled “MOBILE THREE-LEAD CARDIACMONITORING DEVICE AND METHOD FOR AUTOMATED DIAGNOSTICS,” which is acontinuation of U.S. patent application Ser. No. 15/632,155, filed Jun.23, 2017, titled “MOBILE THREE-LEAD CARDIAC MONITORING DEVICE AND METHODFOR AUTOMATED DIAGNOSTICS,” now U.S. Pat. No. 10,117,592, which is acontinuation of U.S. patent application Ser. No. 15/096,159, filed Apr.11, 2016, titled “MOBILE THREE-LEAD CARDIAC MONITORING DEVICE AND METHODFOR AUTOMATED DIAGNOSTICS,” now U.S. Pat. No. 10,433,744, which claimspriority to U.S. Provisional Patent Application No. 62/145,431, filedApr. 9, 2015, titled “MOBILE THREE-LEAD CARDIAC MONITORING DEVICE ANDMETHOD FOR AUTOMATED DIAGNOSTICS,” both of which are incorporated hereinby reference in their entirety.

INCORPORATION BY REFERENCE

All publications and patent applications mentioned in this specificationare herein incorporated by reference in their entirety to the sameextent as if each individual publication or patent application wasspecifically and individually indicated to be incorporated by reference.

FIELD

Described herein are methods and apparatuses for recording bioelectricsignals. More particularly, described herein are hand held apparatuses(devices and systems) for recording, processing and transmitting of ECGdata via commercial network to a remote PC computer for automatedanalysis and generation of information on ECG status and providingfeedback information to the handheld device.

BACKGROUND

Acute Myocardial Infarction (AMI, also referred to as heart attack)remains a leading cause of mortality in the developed world. Findingaccurate and cost-effective solutions for AMI diagnosis is vital.Survival of patients having AMI may depend critically on reducingtreatment delay, and particularly reducing the time between symptomsonset and medical treatment time. A technology that would enable AMIdiagnosis early after occurrence of AMI symptoms, for example, atpatient's home or where ever the patient may be, may significantlydecrease AMI mortality.

In the AMI setting, the conventional 12-lead ECG is not only the mostimportant piece of information, but it is also nearly as important asall other information combined. Therefore, a technology for early AMIdiagnosis may rely on ECG recording. The ECG recording may be performedby the patient himself, but such a technology would need to overcome theproblem of complicated application of 12-lead ECG electrodes, and toenable automated software based AMI detection.

Electrocardiogram (ECG) data recording as acquisition of bioelectricsignals for cardiac condition status detection is widely known in theart. In general, before the recording is performed, characteristicpoints on patient's body are identified and electrodes are positionedwith respect to these points. During the recording procedure, theelectrical voltages between two characteristics points are measured, andcorresponding signals are called ECG leads. The conventional ECG uses 10electrodes to record 12 leads, and the 12 leads ECG (12L ECG) is widelyadopted standard in cardiac diagnostics.

It has long been suggested that urgent cardiac diagnostics which enablesa patient, wherever he may be, to record his ECG himself and send it tohis cardiologist in the remote diagnostic center via commercialtelecommunication network (cellular or similar) would be beneficial. Onthe bases of the received ECG and the conversation with the patient, thecardiologist on duty could decide whether the patient's state requiresurgent medical intervention, and act accordingly. There are a number ofpatents and products which, within the said concept of urgent cardiacdiagnostics, offer different solutions for recording and transmittingthe ECG signal. The simplest of these devices uses only a single ‘lead’or pair of electrodes. However, devices recording only one ECG lead maybe used only for rhythm disorders. Because the ECG changes needed fordetection of an AMI may occur in as few as only two among 12 leads of aconventional ECG, it may be difficult, to reliably use only a singlelead (or in some cases only a few leads) to reliably and thoroughlydetect AMI. Further, it is also unreasonable for a patient to record afull 12L ECG by himself, because of the difficulty in placing the leads.

Solutions capable of detecting AMI that use different surrogates of 12LECG are also known. For example, Heartview P12 by Aerotel (AerotelMedical Systems, Holon, Israel), Smartheart, by SHL (SHL Telemedicine,Tel Aviv, Israel) and CardioBip (e.g., U.S. Pat. No. 7,647,093). Allthese solutions have significant drawbacks. For example, all of thesesolutions typically require complicated measuring procedures (such aswith Heartview, Smartheart), and may require attaching electrodes by themeans of cables, taking the clothes off from the waist up, using strapsand multi-step recording procedure (e.g., see US20120059271A1 to Amitaiet al.). Existing or proposed systems may also require extensivecalibration procedures (e.g., Cardiobip), requiring the patient to be ina medical facility with specially trained personnel prior to using thedevice by himself. Finally, all of these procedures may require medicalpersonnel for interpretation of recorded ECG.

For example, the Cardiobip device is the simplest for use by thepatient, and allows simple positioning of the device by pressing itagainst the chest, with no cables or straps, and recording the ECG. Inthis example, a diagnostic center may use a PC computer withcorresponding software for processing of three special ECG leads andreconstruction of the three leads into a standard 12 lead ECG. Thereconstruction is required for interpretation of ECG by the medicalpersonnel. Accuracy of the reconstruction of a 12 standard ECG leadsusing the recordings of three special leads may be achieved by strictlydetermined arrangement of integrated electrodes in the mobile device andcorresponding leads. A hand-held device may include 5 built inelectrodes (see, e.g., EP1659936) three of which may be placed incontact with the chest of the patient and the remaining two electrodesin contact with right and left hand fingers. The reconstructionalgorithm in the Cardiobip device is premised on the assumption that thediffuse electric activity of the heart muscle can be approximated by atime-changing electrical dipole (heart dipole) immersed in a lowconducting environment. The Heart dipole is represented by a vectordefined by three non-coplanar projections, so that it can be determinedon the basis of recording of electric potential between any three pairsof points corresponding to three non-coplanar directions, i.e., threespecial ECG leads not lying on the same plane. Standard ECG leads arereconstructed as linear combinations of the recorded special leads andcoefficients by which the transformation matrix is defined. It can beshown, by an in depth analysis, that there are two dominant errorsources in such reconstruction. Unfortunately, the heart dipole is onlythe first term in the multipole mathematical expansion of diffuse heartelectrical activity and this approximation is valid only for recordingpoints at a sufficient distance from the heart. In the points near theheart, the linearity of the system necessary for signal reconstructionis significantly affected by the non-dipole content created due to thepresence of higher order terms in multipole expansion.

Further the described reconstruction techniques for converting a fewleads into a 12 lead signal for analysis by a cardiologist or othertechnical expert are also limited. In order to carry enough diagnosticinformation the three special leads need to be as close to orthogonal aspossible (e.g., three vector axis with 90 degrees angle between each ofthem). The opposite to orthogonal is the case of three coplanar vectors,that is three vectors in the same plane, in which case the diagnosticinformation corresponding to the axis perpendicular to that plane iscompletely missing. Importantly the assumptions needed for thismodeling, treating the heart as a dipole (and estimating at a distance)and making orthogonal measurements of the heart leads, are at odds witheach other, since the orthogonal lead positions are far easier to obtainif the electrodes are closer to the heart, while in this case thenon-dipole content is higher. Existing systems such as Cardiobip mustrely on the use of a configuration that optimally fulfills bothrequirements, in which all three leads use the right hand electrode as areference. These systems also have additional drawbacks. For example,Cardiobip uses three integrated electrodes on the chest side of thedevice. It was observed in clinical studies using Cardiobip that breastin female patients and pronounced pectoralis muscle in male patients mayprevent a reliable contact of all three electrodes with the chestsurface simultaneously. It has also been observed that the symmetricalarrangement of finger electrodes on the front side of the device maycause switching of left and right hand fingers in about 10% recordings,making the recording useless for diagnostics.

Similarly, other solutions that use a reduced set of three leads (e.g.,US20140163349A1; US20100076331) typically use the three leads that arecoplanar and therefore lack enough diagnostic information for AMIdetection.

In addition, the requirement for trained medical personnel for theinterpretation of recorded ECG may be an organizational challenge andincreases the operational cost of the system, and the accuracy of thehuman ECG interpretation may have large variance. Automated software forECG interpretation is also used in the systems for early diagnosis ofAMI, but they have performance that is inferior to that of humaninterpreters. The chest pain is the main symptom suggesting an AMI, orischemia (the underlying physiological process). The main ECG parameterused is the ST segment elevation (STE). Unfortunately, a large number ofpatients (up to 15%) presenting with chest pain have STE of non-ischemicetiology (NISTE) on their presenting (to the emergency room) ECG. Thus,both human readers and automated software may often misinterpret NISTEas a new STE due to ischemia. In a typical emergency room (ER) scenario,patients with chest pain are examined by emergency physician who mustpromptly decide if the acute ischemia is present, relaying just on theon-site (current) ECG recording.

Thus, it would be advantageous to provide a technology capable ofseparating new from old STE, as it could significantly increaseperformance of automated AMI detection, and make it a viable enhancementor even replacement for human interpretation, particularly whenqualified human interpretation is not available. Described herein aremethods and apparatuses that may address the problems and needsdiscussed above, particularly the need for early automated remotediagnostics of AMI. In particular the methods and apparatuses describedherein may provide a mechanically stable and improved electricalcontact, while eliminating errors associated with switching of fingercontacts.

SUMMARY OF THE DISCLOSURE

In general, described herein are methods and apparatuses for recordingand analyzing cardiac signals to automatically detect one or moreindicators of cardiac dysfunction, including in particular AMI. Theseapparatuses may typically include a housing having at least fourelectrodes arranged thereon in an asymmetric manner on two or moresurfaces to provide orthogonal, or quasi-orthogonal leads.

As used herein, a cardiac signal may refer to a voltages produced by ahuman heart as sensed between selected points on the surface of asubject's body, and may also be referred to as cardiac electricalsignals (e.g., electrocardic signals). These cardiac signals may includeelectrocardiogram (ECG) signals. It should be understood that althoughthe term ECG (electrocardiogram) is commonly used to refer toconventional 12-lead ECG signals, the cardiac signals (cardiacelectrical signals) described herein are not limited to theseconventional 12-lead ECG signals. Further, although the disclosureherein may use and refer to terms including characteristic points (suchas P,Q,R,S,T) and intervals (such as ST segment) on the cardiac signalsdescribed, these characteristic points may refer to points, positions orregions equivalent to the positions on conventional 12-lead ECG signals.

Described herein are mobile, hand-held apparatuses for automated cardiacelectrical signal analysis. For example, an apparatus may include: ahousing having a back, a first side, and a front; a first electrode anda second electrode integrated on the back of the housing configured tomeasure bioelectric signals from a patient's chest, wherein the firstand second electrode are positioned a distance of at least 5 cm apart; athird electrode configured to measure bioelectric signals from thepatient's right hand; a fourth electrode configured to measurebioelectric signals from the patient's left hand; wherein one or both ofthe third electrode and the fourth electrode are integrated on the frontof the housing; and a processor within the housing configured to recordthree orthogonal cardiac leads from the first, second, third and fourthelectrodes, wherein less than three pairs of said electrodes comprisethe third electrode.

Alternatively or additionally, any of these apparatuses may include: ahousing having a back, a first side, and a front; a first electrode anda second electrode integrated on the back of the housing configured tomeasure bioelectric signals from a patient's chest, wherein the firstand second electrode are positioned a distance of at least 5 cm apart; athird electrode configured to measure bioelectric signals from thepatient's right hand; a fourth electrode configured to measurebioelectric signals from the patient's left hand; and a processorconfigured to record 3 orthogonal cardiac leads from the first, second,third and fourth electrodes, wherein the processor comprises a registerconfigure to store a first set of three orthogonal cardiac leads takenat a first time, and a comparator configured to determine a differencesignal between the first set of three orthogonal cardiac leads and asecond set of three orthogonal cardiac leads taken at a second time.

For example, described herein are mobile, hand-held, three-leadapparatuses for automated electrical cardiac-signal analysis. Anapparatus may include: a housing having a back, a first side, and afront, wherein the front is parallel with the back; a first electrodeand a second electrode integrated on the back of the housing configuredto measure bioelectric signals from a patient's chest, wherein the firstand second electrode are positioned a distance of at least 5 cm apart; athird electrode configured to measure bioelectric signals from thepatient's right hand; a fourth electrode configured to measurebioelectric signals from the patient's left hand; wherein one or both ofthe third electrode and the fourth electrode are integrated on the frontof the housing; a resistive network connecting at least two of thefirst, second, third and fourth electrodes, wherein the resistivenetwork forms a central point (CP); a processor within the housingconfigured to record 3 orthogonal, or quasi-orthogonal cardiac leadsfrom the first, second, third and fourth electrodes, wherein less thanthree pairs of said electrodes comprise the third electrode; and acommunication circuit within the housing configured to transmit the 3cardiac leads to an internal or remote processor.

At least one lead may be formed between one of the said electrodes andthe central point (CP)formed by mutually connecting at least twoelectrodes by the resistive network. For example, the third and fourth(right and left hand) electrodes may be separated by a resistive networkto form a central point so that at least one lead including the thirdand fourth electrodes may be measured between the central point and thethird or fourth electrode.

In general, the apparatus may be oriented, e.g., including an up anddown, relative to the patient's body. The apparatus may include a marker(e.g., one or more of: alphanumeric marker, e.g., label, body shape,light, e.g., LED, etc.). For example, the apparatus may include a markeron the housing indicating the orientation of the housing, such as an LEDmarker on the housing indicating the orientation of the housing.

The third and fourth electrodes may be disposed on two opposed sideswith respect to a longitudinal plane of symmetry of the device housing,said plane of symmetry being substantially perpendicular to the backsurface of the device housing.

In any of these variations, a ground electrode may be present on thehousing for contacting one of the patient's hands disposed on either theside or front of the housing.

Either the third or fourth electrodes may be band-shaped and disposedalong the side of the device housing.

The housing may comprise a mobile phone housing, whereby the third orfourth electrodes are configured as conductive transparent areas on thetouch screen of the mobile phone. The housing may be incorporated in amobile phone housing. The housing may be an extension structure of amobile phone housing communicating with the said phone using anelectrical connector or wireless communication. The housing may formamobile phone protective case. For example, the housing may forma mobilephone protective case with a phone display protective cover and thethird and fourth electrodes incorporated in the phone display protectivecover.

In some variations, the apparatus is integrated with or connected to acover (e.g., back cover) of a mobile phone. For example the housing forthe apparatus may be a back cover for a mobile phone that can beretrofitted (e.g., used to replace) a standard back cover of asmartphone or other mobile phone. In some variations, the apparatus canbe connected to the cover (e.g., back cover) of the mobile phone, e.g.,by an adhesive or other attachment mechanism.

Also described herein are methods of detecting cardiac anomalies, suchas detecting ischemia, atrial fibrillation or other cardiac disorder;these methods may be automated methods. Any of these methods may bemethods for automated cardiac diagnostics, and may include: acquiring afirst set of at least three orthogonal leads from a patient's chest andhands at a first time; acquiring a second set of at least threeorthogonal leads from the patient's chest and hands a second time;performing a beat alignment in a processor on the first and second setsof at least three orthogonal leads to synchronize representative beatsfrom the first and second sets of at least three orthogonal leads;calculating a difference signal representing the change between thefirst and second at least three orthogonal leads; detecting cardiacchanges suggestive of a cardiac condition by comparing parameters of thefirst and second at least three orthogonal leads or by comparingparameters of the difference signal to a predefined threshold; andcommunicating cardiac changes from the device to the patient.

Alternatively or additionally, a method for automated cardiacdiagnostics may include: positioning a device configured to detect atleast three orthogonal leads from a patient's chest and hands againstthe subject's chest in a first recording position; acquiring a first setof at least three orthogonal leads from the device at a first time;communicating the first set of at least three orthogonal leads to aprocessor; positioning the device against the subject's chest in asecond recording position; acquiring a second set of at least threeorthogonal leads from the patient using the device at a second time;communicating the second set of at least three orthogonal leads to theprocessor; performing a beat alignment in the processor to synchronizerepresentative beats from the first and second sets of at least threeorthogonal leads; calculating a difference signal representing thechange between the first and second sets of at least three orthogonalleads; detecting cardiac changes suggestive of a cardiac condition bycomparing one or more parameters of the difference signal to apredefined threshold; and communicating cardiac changes from the deviceto the patient.

For example, a method for automated cardiac diagnostics may include:placing a device comprising a housing having four integrated electrodesarranged to measure three orthogonal leads from a patient's chest andhands against the subject's chest in a first recording position;acquiring a first 3 lead cardiac recording (also referred to as threecardiac lead recording and three lead electrical cardiac readings) fromthe device at a first time (e.g., taking a baseline recordings);communicating the first 3 lead recording to a processor; keeping thedevice at the same first recording position or placing the deviceagainst the subject's chest in a second recording position; acquiring asecond 3 lead recording from the device at a second time (diagnosticrecordings); communicating the second 3 lead recording to the processor;performing a beat alignment in the processor to synchronizerepresentative beats from the first and second 3 lead recordings;calculating a difference signal representing the change between thefirst and second 3 cardiac leads recordings; detecting changes in thecardiac signals (e.g., changes in the cardiac signal records, alsoreferred to herein as cardiac changes) suggestive of cardiac conditions,such as ischemia or atrial fibrillation, by comparing parameters of thefirst and second 3 lead cardiac recording or by comparing parameters ofthe difference signal to a predefined threshold; and communicating anycardiac changes suggestive of a cardiac condition from the device to thepatient.

The first and second recording positions may be different or the same.In some variations, the method (or an apparatus performing the method)may detect if the positions have changed and either correct for thedifferent recording positions or indicate that the hand-held deviceneeds to be more accurately repositioned. For example, the method mayinclude compensating for chest electrode miss-positioning between thefirst and second recording positions in the processor by compensating aheart electrical axis deviation in a 3 cardiac leads vector space.

Communicating the first 3 lead electrical cardiac recording to theprocessor may comprise wirelessly transmitting the first 3 leadelectrical cardiac recordings to a remote processor, transmitting apartial cardiac-recording processing result to a remote processing, orjust transferring the 3-lead cardiac recordings to an internal processorfor processing, or for patient alert.

In general, these methods may include pre-processing the first andsecond 3 lead electrical cardiac recordings in the processor to achieveone or more of: eliminate power line interference, baseline wanderingand/or muscle noise; obtain a representative beat using fiducial pointsand median beat procedure; and check for switching of the left and rightfinger.

The parameters of the diagnostic recording, baseline recording anddifference signal may be vector magnitude of the cardiac signal, wherethe vector components are three cardiac leads of the diagnostic,baseline and difference signals in a single time instant (J point, J+80ms) or average in predetermined time interval (e.g., the ST segment orother predetermined interval) and radius of the sphere which envelopesthe vector signal hodograph of the ST segment (or other predeterminedinterval).

The parameters of the diagnostic recording, baseline recording anddifference signal may be RR variability (or equivalent), amplitude of Pwaves (or equivalent), or averaged amplitude of P waves when detectionof atrial fibrillation or atrial flutter are desired.

Any of these methods may also include transmitting any cardiac signalchanges suggestive of a cardiac condition from the processor to thedevice. The methods may also include communicating any cardiac signalchanges suggestive of a cardiac condition from the device to the patientcomprises presenting a visual and/or audible alert to the patient.

For example, a method for automated cardiac diagnostics may include:placing a device comprising a housing having four integrated electrodesarranged to measure three orthogonal, or quasi-orthogonal, leads from apatient's chest and hands against the subject's chest in a firstrecording position; acquiring a first 3 lead cardiac recording from thedevice at a first time; communicating the first 3 lead cardiac recordingto a processor; storing the first 3 lead cardiac recording as baselinerecording; keeping the device at the same first location, or placing thedevice against the subject's chest in a second recording position;acquiring a second 3 lead cardiac recording from the device at a secondtime; communicating the second 3 lead cardiac recording to theprocessor; pre-processing the first and second 3 lead cardiac recordingsin the processor to eliminate power line interference, baselinewandering and muscle noise, obtain a representative beat using fiducialpoints and median beat procedure, and to check for switching of the leftand right finger; performing beat alignment in the processor to bringrepresentative beats from the first and second 3 lead cardiac recordingsin a same time frame so that corresponding points are synchronized;compensating for chest electrode miss-positioning between the first andsecond recording positions in the processor by compensating a heartelectrical axis deviation in a 3 cardiac leads vector space; calculatinga difference signal representing the change between the first and second3 cardiac leads recordings; detecting cardiac signal changes suggestiveof cardiac condition (e.g., ischemia, atrial fibrillation, atrialflutter, etc.) by comparing parameters of the first and second 3 leadcardiac recording or by comparing parameters of the difference signal toa predefined threshold; communicating any cardiac signal changessuggestive of a cardiac condition from the device to the patient.

In general, described herein are apparatuses configured to perform anyof the methods described herein. For example, an apparatus configured toprovide an automated cardiac diagnostics may include: a housingcomprising at least four electrodes connected to a processor within thehousing; wherein the processor is configured to: acquire a first set ofat least three orthogonal leads from a patient's chest and hands at afirst time; acquire a second set of at least three orthogonal leads fromthe patient's chest and hands a second time; perform a beat alignment onthe first and second sets of at least three orthogonal leads tosynchronize representative beats from the first and second sets of atleast three orthogonal leads; calculate a difference signal representingthe change between the first and second at least three orthogonal leads;detect cardiac changes suggestive of a cardiac condition by comparingparameters of the first and second at least three orthogonal leads or bycomparing parameters of the difference signal to a predefined threshold;and communicate cardiac changes from the device to the patient.

Although the description of the methods and apparatuses included hereindescribes the use of a set of orthogonal, or quasi-orthogonal, cardiacsignals, these methods and apparatuses may be used with any set ofsignals (cardiac electrical signals) which contain significantindependent cardiac information. For example, an implementation thatused cardiac leads represented by vectors that are not completelyorthogonal would not deviate from the spirit of this invention. It wouldbe important to have the respective cardiac vectors orientated atrelative angles greater than 30° with respect to one another. Suchsmaller relative angles may still provide significantly linearlyindependent information and allow the apparatuses and methods describedherein to produce similar and clinically/diagnostically relevantresults. Accordingly, for simplicity, without implying any limitation,we may herein refer to our cardiac leads as orthogonal leads. Thus,orthogonal leads may be strictly orthogonal (e.g., having deviation ofthe leads relative angles from 90° less than 10°, less than 8°, lessthan 7°, less than 6°, less than 5°, less than 4°, less than 3°, lessthan 2°, less than 1°, etc.) or approximately orthogonal (e.g., havingdeviation of the leads relative angles from 90° less than 30°, 25°, 20°,15°, etc.). Alternatively, the quasi-orthogonality can be assessed basedon the cross-correlation function of combinations of data from any twoleads, data which were required at about the same time and with the samedevice. Given that herein orthogonality refers to the amount ofindependent information content, two leads from the set may be deemedquasi-orthogonal if there cross-correlation is less than 0.6.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows one variation of a schematic configuration of a diagnosticsystem for detection of cardiac disorders such as AMI, including a localprocessor in the system.

FIG. 1B is another schematic of a remote diagnostic system, wherein theprocessor is remote from the hand-held device.

FIG. 2A shows a front (non-chest) view of one variation of a handhelddevice with two recording and one ground electrode.

FIG. 2B shows a back (chest) view of one variation of a handheld devicewith two recording electrodes.

FIG. 2C shows an axonometric view of a handheld device.

FIG. 2D shows a front view of the device placed against the patient'sbody in a recording position.

FIG. 3 shows a simple electrical scheme for obtaining a central point CPby connecting the electrodes of both hands via a simple resistivenetwork with two resistors.

FIG. 4A shows schematic configuration of the three cardiac leadsmeasured on the torso with one lead using central point as the referencepole—the preferred embodiment.

FIG. 4B shows an electrical circuit of the three cardiac leads with onelead using central point as the reference pole.

FIG. 4C shows a schematic configuration of the three cardiac leadsmeasured on the torso with two leads using central point as thereference pole.

FIG. 4D is an electrical circuit of the three cardiac leads with twoleads using central point as the reference pole.

FIGS. 4E, 4F and 4G show schematic diagrams of three possibleconfigurations for measuring 3 leads among two chest and two handelectrodes.

FIG. 5A shows a front (non-chest) view of the handheld device with twofront and one side electrode.

FIG. 5B shows a back (chest) view of the handheld device with two frontand one side electrode.

FIG. 5C shows an axonometric view of the handheld device with two frontand one side electrode.

FIG. 6A is a front (non-chest) view of the handheld device withelectrodes on the edges of the device.

FIG. 6B is a back (chest) view of the handheld device with electrodes onthe edges of the device.

FIG. 6C is an axonometric view of the handheld device with electrodes onthe edges of the device.

FIG. 7 is an axonometric view of the handheld device realized as a flipcase attachable to a mobile phone.

FIG. 8 shows a flow chart of the method for detecting AMI.

FIG. 9 shows one example of a patient with BER (Benign EarlyRepolarization), showing median beats in 12 leads. Both pre-inflationand inflation recordings show ST segment elevation in precordial leads,which is typically problematic for a human reader to distinguishischemic from non-ischemic recording.

FIG. 10 is an example of a patient with BER (Benign EarlyRepolarization), showing median beats in 3 special leads. The signaldifference between pre-inflation and inflation recordings enables thealgorithm to distinguish ischemic from non-ischemic recording.

DETAILED DESCRIPTION

Described herein are apparatuses (including devices and systems) andmethods for remote diagnostics of cardiac conditions, such as acutemyocardial infarction (AMI), atrial fibrillation (AFib), or the like. Inparticular, described herein are handheld devices with special electrodeconfigurations capable of recording three orthogonal cardiac leadsignals in an orientation-specific manner, and transmitting thesesignals to a processor (e.g., PC or other computing device). Theprocessor may be configured to diagnose/detect AMI and transmit thediagnostic information back to the handheld device. The handheld devicemay communicate the diagnostic information to the patient viacharacteristic sounds, voice massages or via a graphical display. Theprocessor may be configured via hardware, software, firmware, or thelike, and may process the signals received to produce a differencesignal and extract information reliably related to detection of AMI (andadditional information of clinical relevance). Thus, these apparatusesand methods may perform automated detection of cardiac conditions on thebasis of a 3-lead system, without the necessity for 12L ECGreconstruction, reducing or eliminating the need for medical personnelto interpret the ECG, unlike prior art systems, which typically rely onmedical personnel for such decisions. The automated diagnostic methodsdescribed herein, in combination with the improved handheld cardiacdevices, address many of the needs and problems present in othersystems.

Specifically, described herein are 3-lead cardiac recording devices foruser placement on the chest, which include an arrangement of electrodeson both the front and back (and in some variations, one or more sides)so that the devices may be held by both of the user's hand in apredefined orientation, so as to record a 3 lead cardiac signals whenheld against the user's chest. In order to fulfill above describedfunctions, the handheld device may record three leads without usingcables (e.g., may include only surface electrodes held or held againstthe body). Further, the resulting three leads are non-coplanar, and asclose to orthogonal as possible. Finally, at least one electrode may bemounted on the front side of the device (opposite to the chest side), toproduce the force needed to hold device against the chest. Unlike priorart devices, there is no requirement for low, non-dipolar content, asthe apparatuses and methods described herein do not requirereconstruction of 12L ECG from the measured 3 leads.

The handheld devices described herein are configured to be mechanicallystable and allow good electrical contact with the chest and to eliminatepossibility for switching of finger contacts. The handheld devicesdescribed herein may include five electrodes, e.g., four recordingelectrodes and one ground electrode. Typically, the handheld device mayinclude two chest electrodes which are the recording electrodes, and maybe located on the back side of the device. The remaining three non-chestelectrodes may be used for collecting cardiac signals from the fingersof the right and left hand and the third one may be used as the groundelectrode. At least one of these three non-chest electrodes may bemounted on the front side for pressing with the fingers in order toproduce enough pressure to hold the device against the chest. Finally,the requirement of avoiding finger switching may be fulfilled by anasymmetric electrode configuration. For example, one of the threenon-chest electrodes may establish contact with one finger of the firsthand, and the remaining two electrodes may establish contact with theother hand. One of these two electrodes may be used as common groundelectrode and the other may be used for signal measuring. An example ofsuch configuration has two chest recording electrodes, one recordingfinger electrode on the left side of the device and two fingerelectrodes on the front side of the device, one recording and one groundelectrode. The optimal position of the handheld device on the chest iswith center of the device on the left side of the chest approximatelyabove the center of the heart muscle. In this position, the chestelectrodes are approximately on the midclavicular line, the verticalline passing through the midpoint of the clavicle bone, same as for theV4 electrode of the conventional ECG, and the lower chest electrode isat about the level of the lower end of the sternum.

In another embodiment, the ground electrode may be excluded from theconfiguration, which may give acceptable 50-60Hz electrical noiseperformance if a ground-free signal amplifier configuration is used. Afour recording electrode configuration (having two chest and two fingerelectrodes) may also fulfill the condition of high orthogonalitydiscussed above. The simplest way to fulfill this requirement is torecord signals in three main body directions: lateral (left arm-rightarm), sagittal (back-front) and caudal (head-toes). For example, thesignal in the lateral direction may be obtained by measuring the leadbetween left and right hand. The signal in the caudal direction may beobtained by measuring the lead between the two chest electrodes, withthe condition that the distance between the chest electrodes in caudaldirection is at least 5 cm, preferably greater than about 10 cm, inorder to be greater than the approximate diameter of the heart muscle.In an ideal case, the signal in the sagittal direction would be measuredbetween the back and the chest of the patient, which is not possiblewith the constraint of using only finger and chest electrodes. Toovercome this, we use a simple resistive network to make a central point(CP) that is close to the heart electrical center. For recording a leadin approximately sagittal direction, we record the voltage of the lowerchest electrode with respect to a central point (CP), obtained using twohand electrodes and two resistors. The two resistors may be equal,approximately 5 kΩ each, or unequal, the first one approximately 5 kΩbetween the left hand electrode and the CP, and the second oneapproximately 10 kΩ between the right hand electrode and the CP. Thisasymmetry reflects the left-side position of the heart in the torso,thus shifting the CP at the approximate electrical center of the heart.In this way we obtain a three lead system that are substantiallyorthogonal.

Other similar lead configurations with the same CP may be chosen usingthe same set of two chest and two hand electrodes, with the distancebetween the chest electrodes in caudal direction at least 5 cm,preferably greater than about 10cm. Such a lead configuration may besubstantially orthogonal, for example when both chest electrodes areused to record leads with the reference pole at the CP. Anotherpossibility to define CP is using three electrodes, two hand electrodesand one chest electrode, and 3 resistors connected in a Y (star)configuration.

Other lead configurations without CP may also be used, like theconfiguration recording the signal of two chest electrodes and righthand electrode with respect to left hand electrode. Such configurationswithout resistors or CP are more noise resistant to, for example,50-60Hz electrical noise, but have less orthogonal lead directions thanthe described ones using a CP. Generally, any other lead configurationusing the same four described electrodes (a total of 20 configurationswithout a CP) results in leads that are non-coplanar and as such capturediagnostic signal in all three directions, but may lack a high degree oforthogonality. However, these configurations may have different levelsof orthogonality, depending on the use of the right hand electrode. Theconfiguration using the right hand electrode as the common referencepole in all 3 leads may have the lowest orthogonality, since the righthand electrode is farthest from the heart among the four electrodes, andthus the angles between the vectors corresponding to the three leads arethe smallest. The configurations using right hand electrode in two leadshave better orthogonality, while best orthogonality is achieved in theconfigurations using right hand electrode in only one lead.

The effectiveness of the described solution is not affected if one ormore chest electrodes are added on the back side of the device, and oneor more corresponding additional leads are recorded and used indiagnostic algorithms. Also, the effectiveness will not be affected iffront electrodes are pressed with palms or any other part of handsinstead with the fingers.

In order to prevent turning the device upside down during the recordingprocedure, so that the upper side is facing toes of the patient, insteadof facing his head, which would lead to a useless recording, eitherupper or front side of the device may be clearly identified and/orformed, (including being marked) to be easily distinguishable by thepatient, for example by a LED diode indicating the current phase ofrecording.

The handheld cardiac device may be configured as a stand-alone deviceincorporating an ECG recording module including amplifiers and ADconvertor, data storage module, communication module operating on GSM,WWAN, or a similar telecommunication standard for communication with theremote processor (e.g., PC computer, pad, smartphone, etc.) andcircuitry (e.g., Wi-Fi, Bluetooth, etc.) for communicating thediagnostic information to the user. Alternatively, it can be realized asa modified mobile phone that includes measuring electrodes and therecording module. Furthermore, it can be realized as a device that isattached to the mobile phone as a case or interchangeable back cover.The attached device incorporates measuring electrodes and the recordingmodule and communicates with the mobile phone using a connector or awireless connection such as Bluetooth or ANT.

If the device is configured as modified mobile phone or as a deviceattached to a mobile phone, the hand electrodes may be mounted on thedisplay side of a mobile phone. The hand electrodes can be integrated inthe edges of the display side of the phone, or as conductive areasincorporated in a transparent layer covering the display of the phone,arranged in the same way as hand electrodes in the preferred embodiment,and marked with a special color when an cardiac signals measuringapplication is active.

The signal processing and diagnostic software can also be run on theprocessor (e.g., microprocessor) including a processor integrated in thehandheld device, instead of running on a remote processor (e.g., PCcomputer). In this case, the communication of recorded information tothe remote computer may no longer be required, except for data andprocessing backups. Also, when the diagnostic processing is carried outby a remote processor, a backup version of the software running on themicroprocessor may be integrated in the handheld device, and may be usedin situations when the user is in a zone without wireless networkcoverage.

Also described herein are methods and apparatuses for automateddetection of AMI (or ischemia, the underlying physiological process).These automated systems may include three cardiac leads that aresubstantially orthogonal contain the majority of diagnostic informationthat is present in the conventional 12-lead ECG. Each user may beregistered in the diagnostic system by performing the first transmissionof his/her non symptomatic cardiac recording with 3 cardiac leads. Thisfirst recording may be used as a reference baseline recording for AMIdetection in the diagnostic recording (diagnostic recording meaning anyfurther recording of the 3 cardiac leads of the same user). Theavailability of the reference baseline cardiac recording may allowdistinguishing new from old STE (or equivalent parameter), and alsoother cardiac signal changes suggesting an AMI, providing a tool forautomated AMI detection that may have diagnostic accuracy comparable tohuman ECG interpreters.

The optimal placement of the handheld devices described herein istypically on the chest is with center of the device on the left side ofthe chest approximately above the center of the heart muscle. In thisposition, the right edge of the device may be about 3 cm away from themidsternal line, the vertical middle line of the sternum, and the loweredge of the device is at about level of the lower end of the sternum. Inan ideal case, the user chooses the optimal position on the chest in thefirst baseline recording and repeats this position in each futurediagnostic recording. In such situation, the cardiac recordings arerepeatable, and it is easy to detect cardiac signal changes suggestingan AMI.

In some variations, an adhesive may be used. Thus the apparatus mayinclude an adhesive material or an adhesive patch or dock may be used toconnect to reproducibly connect to the apparatus and hold it in apredetermined position on the user. For example, the same recordingposition of the electrodes during the baseline recording and any furthertest recording can be achieved using a self-adhesive patch with (orconnecting to a device with) the chest electrodes. A self-adhesive patchwith the chest electrodes may be attached for the first recordings andremains on the same place on the user chest. Similarly, a patch to whichthe apparatus may dock to place the electrodes in a predeterminedlocation may be used. The user needs to touch the hand electrodes.

In a realistic case, the user may place the device at a position that isdifferent compared to the baseline position, which may compromisediagnostic accuracy. This misplacement is equivalent to a virtual changeof the heart electrical axis in the 3D vector space defined by the 3cardiac leads. In some variations, this angular change may be calculatedfor each test recording compared to baseline recording. If the angularchange is greater than a threshold, such as 15 degrees, the user may bealerted to choose a position that is closer to the baseline position. Ifthe change is lower than the threshold, it may be compensated for byrotating the signal loops of the test recording in the 3D vector spaceand get the signal that is substantially equivalent to the baselinesignal.

Although switching of the left and right finger or turning the deviceupside down is not very likely (due to asymmetric electrodeconfiguration and configuration of the apparatus, e.g., by clear markingof the upper or front side of the device), it may still be possible. Inthis case all three signals may become unusable. Both of these usererrors may be easily detected, since in both cases the signal of thelead recorded between the left and the right hand may become inverted.In such case, the user may be alerted to repeat the recording using thecorrect recording position.

The method for automated detection of AMI (or ischemia) may, in somevariations, the following steps: placing the device in a recordingposition on the user chest; acquisition of a first 3 lead cardiacrecording and communicating the signals to the processing unit; storageof the first recording in the data base of the processing unit asbaseline recording for further comparison with any subsequent diagnosticrecording; acquisition of the 3 lead cardiac diagnostic recording andcommunicating the signal to the processing unit, and processing of theresulting signals. Processing of the stored baseline signals and signalsof the diagnostic recordings by the processing unit may include thefollowing steps: pre-processing to eliminate power line interference,baseline wandering and muscle noise, obtain representative beat usingfiducial points and median beat procedure, check for switching of theleft and right finger, beat alignment to bring baseline and testrecordings' representative beats in the same time frame so as thecorresponding points are synchronized, compensation for chest electrodemispositioning in recording the test signal by compensating the heartelectrical axis deviation in the 3 cardiac leads vector space,calculating difference signal, representing the change between baselineand diagnostic 3 cardiac leads signals, detection of cardiac signalchanges suggesting ischemia by comparing the parameters of the testrecording to the baseline recording or by comparing parameters on thedifference signal to a predefined threshold, communicating informationby the processing unit to the device, and finally communicating thediagnostic information by the device to the patient.

The STE (ST segment elevation) is the most common ECG change in case ofischemia, usually measured at the J point or up to 80 msec later. UsingSTE as a parameter, the ischemic changes may be detected by comparingSTE in the test recording to the baseline recording. Also, the ischemicchanges may be detected by measuring the vector difference of the STvector in the vector space defined by the 3 special cardiac leads(STVD), taking the baseline recording as a reference. As mentionedabove, although these parameters (e.g., ST, J, STVD, STE), are definedwith respect to traditional 12-lead ECG signals, they be herein refer toequivalent measures determined for the three cardiac leads (orthogonalsignals) described herein. Thus, these equivalent points, regions orphenomena (e.g., STE, ST, J, STVD, etc.) may be identified by comparisonbetween the cardiac signals described herein and traditional ECGsignals, including traditional 12-lead ECG signals.

Other parameters of the ECG signal may also be used for comparison withthe baseline reference signal, such the “Clew”, defined as the radius ofthe sphere which envelopes the vector signal hodograph between J andJ+80 msec points.

Cardiac signals for an individual are highly repeatable as far as theirshape is concerned. The changes of the signal shape are generally smallfor a healthy, or an individual in stable condition. For example, thechange of the position of the heart with respect to rib cage can changethe heart electrical axis by up to 10°. However, there are conditionswhen the signal shape may change over time, like Benign EarlyRepolarization (BER). Such signal changes are highly individual andcould be significant. To compensate for such changes, a number ofbaseline recordings, taken by the user over a period of time, may beused to form a reference that forms a 3D contour in the vector spacedefined by the 3 special cardiac leads (instead of a single point whensingle baseline recording is used). In using such a 3D contourreference, the ST vector difference (STVD) may be defined as a distancefrom the 3D contour instead from the baseline ST vector. If more thanone parameter is used for ischemia detection, such a reference contourmay be constructed as a hyper-surface in a multidimensional parameterspace defined by such parameters. In this case a hyper-distance from thereference hyper-surface will be defined in the said parameter space.

In some conditions, the signal shape changes may also be intermittent(the condition “comes and goes”), like in Brugada syndrome, WPWsyndrome, Bundle Branch Blocks (BBB), etc. To compensate for signalchanges in such conditions, two groups of baseline recordings (e.g., atleast two recordings) may be used to define the reference, one withnormal signals and one with the said intermittent condition present.These two groups will form two 3D contours in the vector space, forminga reference for comparison. These two 3D contours may overlap or not. Ifthere is no overlap, the ST vector difference (STVD) will be defined asa distance from closest point on the two 3D contours. If more than oneparameter is used for ischemia detection, such reference contours wouldbe constructed as two hyper-surfaces in a multidimensional parameterspace defined by such parameters. In this case a hyper-distance from thereference hyper-surface will be defined in the said parameter space.

Primary use of the methods described herein may be applied to thedetection of the most urgent cardiac diagnosis—the AMI. Additionally,the diagnostic methods (e.g., software) in the remote processor (orintegrated processor in the handheld device) can detect other cardiacconditions such as chronic Coronary Artery Disease (CAD), LeftVentricular Hypertrophy (LVH), Bundle Branch Blocks (BBB), Brugadasyndrome, rhythm disorders such as Atrial Fibrillation (AF) etc.

Although the methods described herein do not require the reconstructionof conventional 12 lead ECG recordings, they may be used to reconstructthem. In many of the above mentioned conditions to be detected,treatment may be urgently needed, although to a lesser extent comparedto AMI. Also, many of such conditions are transient, and may be detectedusing here described technology, but may not be present when the userlater comes to the physician's office. In such a case, it would beuseful to present the ECG signals for the condition that was discoveredat the time of recording, so that physician may use it to confirm thediagnosis. Physicians are familiar with the conventional 12 lead ECGrecording. Therefore, 3 special cardiac leads recorded when thecondition was discovered may be transformed to produce an approximatereconstruction of conventional 12 lead ECG recording. Suchreconstruction may be obtained by multiplication of the 3 specialcardiac leads with a 12×3 matrix. This matrix may be obtained as apopulation matrix, that is a matrix with coefficients that arecalculated as average, or median, values of individual matrices obtainedby simultaneously recording conventional 12 lead ECG and 3 specialcardiac leads in a population of individuals, with each individualmatrix obtained using least squares method. The coefficients of suchmatrices are dependent of the shape of the user's body. Therefore,instead of using a single population matrix, multiple matrices may beused, each for a group of users defined by simple parameters of the bodyshape and structure, like gender, height, weight, chest circumference,etc., that may be easily obtained by the user. Also, matrix coefficientsmay be obtained as continuous functions of such body parameters.

FIG. 1A illustrates one variation of a method of operating a system 2for cardiac signal detection and/or diagnosis. In FIG. 1A, the user mayrecord cardiac signals (e.g., at two or more times), and the apparatusmay process the three orthogonal leads to compare the different times(e.g., baseline vs. assay time). The processor of the apparatus mayfurther determine if the resulting differential signal indicates thatcardiac problem, and can alert the user. The user (patient) can then getmedical assistance as necessary. FIG. 1B shows a view of anthervariations of a system and method for detecting cardiac dysfunction,including a system 1 for remote diagnostics of AMI including handhelddevice 2 incorporating built in electrodes for cardiac signalacquisition, mounted directly on the casing 3 of the hand held deviceand a PC computer 4 connected via a telecommunication link to thedevice.

The device further incorporates an cardiac signal recording circuitryincluding amplifiers and AD convertor for amplifying the signalsdetected by the electrodes, data storage (e.g., memory) for storing therecording signal, communication circuitry operating on GSM, WWAN, or asimilar telecommunication standard for communication with the remoteprocessor 4 and visual and/or audio (e.g., monitor, speaker, etc.) forcommunicating the diagnostic information to the user.

The device may be communicating with the remote processor 4 viaintegrated communication circuitry. The remote processor 4 maycommunicate with the handheld device 2 via integrated communicationmodule. The processor 4 may be equipped with diagnostic software forprocessing the received cardiac signals, producing diagnosticinformation and for transmitting the information back to the handhelddevice for communicating the diagnostic information to the patient viamicrophone producing characteristic sounds or voice messages or in theform of graphical information via a display integrated in the device. Asa consequence, the system may be capable of performing automateddetection of a cardiac condition on the basis of a 3-lead system anddoesn't require interpretation of the processed diagnostic informationby a specialist. Alternatively, instead of a remote processor, thesystem may include a microprocessor integrated in the casing 3 of thehand held device for processing the recorded cardiac signals andproducing diagnostic information.

FIGS. 2A, 2B and 2C show front, back and axonometric views,respectively, of the preferred embodiment of the hand held device. FIG.2A shows the front view of the device 2 in the recording position asheld by the user. The casing 3 of the device may incorporate fourrecording electrodes A, B, C, D, and one ground electrode G arranged insuch arrangement that enables recording of three special ECG leadsignals. On the flat back surface 5 of the device in this example aremounted two recording electrodes, A and B, used to make contact with thechest of the patient in the recording position. The two chestelectrodes, A and B, are preferably arranged to cover distance greaterthan at least 5 cm, preferably greater than about 10cm in caudaldirection. The reason for having such spaced arrangement is to achievethe distance greater than approximate diameter of the heart muscle whichis needed to approach as much as possible lead orthogonality.

In addition to the two chest electrodes, A and B, the device in thisexample has two recording electrodes, C and D, mounted on the flat frontsurface 6 substantially parallel and opposite to the back surface 5.These electrodes, C and D, are used for recording cardiac signals of thehands by pressing with fingers of the left and right hand respectively.The fifth electrode G serves as grounding electrode and is mounted onthe front surface 6 for pressing with a left hand finger.

Referring back to FIG. 2A, there is shown a view of the preferredembodiment of the invention in recording position. For operation, theuser (e.g., patient) places the device in his left hand so thatpatient's index and middle finger contact electrodes C and Grespectively, positions and presses the device against his chest so thatthe chest electrodes A and B contact his chest in the manner shown inFIG. 2E for producing tight contact between chest and the device. Thismay produce enough pressure for holding the device against the chest.Simultaneously, a finger of the right hand (or any other part of theright hand) presses the reference electrode D mounted on the frontsurface 6 of the casing 3.

Referring back to FIG. 2D there is shown a front view of the deviceplaced against the patient's body in recording position according to thepreferred embodiment of the invention. In an optimal recording positionthe center of the device is placed closely above the center of the heartso that the chest electrodes A and B are approximately on themidclavicular line (the vertical line passing through the midpoint ofthe clavicle bone), and the lower chest electrode B is at about thelevel of the lower end of the sternum.

The example in FIG. 3 shows a simple electrical scheme for obtaining acentral point CP by connecting the electrodes of both hands via a simpleresistive network with two resistors.

FIG. 4A shows a spatial view of the lead configuration according to oneembodiment, illustrating the arrangement of active electrodes A, B, C, Dwith respect to the body, as well as relative arrangement between theelectrodes. FIG. 4B shows a simplified electrical scheme illustratingthe same relative arrangement between the electrodes shown in FIG. 4A.For recording a lead in approximately sagittal direction, the voltage ofthe lower chest electrode B with respect to a central point CP may beobtained using the hand electrodes C, D and two resistors R1, R2. Thetwo resistors R1, R2 can be equal, approximately 5 kΩ each, or unequal,approximately 5 kΩ between the left hand electrode and the CP, and 10 kΩbetween the right hand electrode and the CP. This asymmetry may reflectthe left-side position of the heart in the torso, thus putting the CPpoint at the approximate electrical center of the heart. In this way asubstantially orthogonal three lead configuration may be obtained.

FIG. 4C shows a spatial view of an alternative lead configuration withthe central point CP using the same set of chest and hand electrodes A,B, C, D, illustrating arrangement of the electrodes with respect to thebody, as well as relative arrangement between the electrodes. FIG. 4Dshows simplified electrical scheme illustrating the same relativearrangement between the electrodes A, B, C, and D, shown in the FIG. 4C.This alternative lead configuration using a central point CP andmeasuring two leads between the CP and each of the chest electrodes isalso substantially orthogonal, since the chest electrodes A, B are usedto record leads with the reference pole at the CP which is obtainedusing two hand electrodes C, D and two resistors R1, R2.

Other lead configurations without central point CP and resistors mayalso be used, like the configuration shown in FIG. 4E, recording thesignal of two chest electrodes and right hand electrode with respect toleft hand electrode. Other two similar configurations are shown in FIGS.4F and 4G. Such configurations without resistors are subject to lessexternal interference, such as 50-60Hz electrical noise, but have lessorthogonal lead directions than the previously described ones using aCP. Generally, any other lead configuration using the same fourdescribed electrodes may result in non-coplanarity and, as such,captures the diagnostic signal in all three directions, but lacks highorthogonality. There are a total of 20 possible configurations without aCP, including ones shown in FIGS. 4E, 4F and 4G. However, theseconfigurations have different levels of orthogonality, depending on theuse of the right hand electrode. The configuration using the right handelectrode as the common reference pole in all 3 leads have the lowestorthogonality, since the right hand electrode is farthest from the heartamong the four electrodes, and thus the angles between the vectorscorresponding to the three leads are the smallest. The configurationsusing right hand electrode in two leads, such as the configuration shownin FIG. 4F, have better orthogonality, while best orthogonality isachieved in the configurations using right hand electrode in only onelead, such as the configurations shown in FIGS. 4E and 4G.

FIGS. 5A, 5B and 5C show front view, back view and an axonometric view,respectively, of an alternative embodiment of the hand held device,whereby FIG. 5A shows the front view of the device in the recordingposition as held by the user. In the alternative embodiment, theelectrode D1 for recording ECG signal of the right arm by pressing withfinger of the right hand is mounted on the flank 71 of the casing 31,instead on the front surface 61 as in the embodiment described above.Active recording electrodes A1 and B1 for recording ECG signal of thepatient's chest are mounted on the back surface 51 of the device in thesame manner as in the embodiment above. An active recording electrode C1for recording ECG signal of the left hand by pressing with finger of theleft hand and ground electrode G1 for pressing with another finger ofthe left hand are mounted on the front surface 61 also in the samemanner as above.

The finger switching may be prevented by having an asymmetric electrodeconfiguration, so that the right hand electrode cannot be wronglypressed by the left hand, and vice versa. However in each of theembodiments (preferred and alternative), the upper (facing head) andlower part (facing toes) of the device may be easily distinguished,since turning the device upside down would lead to wrong recording. Thismay be done by integrating LED diodes in either upper or front side ofthe device, indicating the current recording phase, in the front surfaceof the device casing.

The handheld cardiac device may be realized as a stand-alone deviceincorporating an ECG recording circuitry including amplifiers and ADconvertor, data storage circuitry (memory), communication circuitryoperating on GSM, WWAN, or a similar telecommunication standard forcommunication with the remote PC computer and an output forcommunicating the diagnostic information to the user (e.g., screen,speaker, etc.). In so embodiments, the apparatus may be configured tooperate with a modified mobile phone that includes measuring electrodesand the cardiac signal recording capability. Furthermore, the apparatuscan be realized as a system that is attached to a mobile phone(smartphone) as a case or interchangeable back cover. The attacheddevice may incorporate measuring electrodes and the cardiac signalrecording module (including electrodes, balancing circuit, etc.) andcommunicates with the mobile phone using a connector or a wirelessconnection such as Bluetooth or ANT.

FIGS. 6A, 6B and 6C show a front view, back view and axonometric view,respectively, of another alternative embodiment of the hand held device.On the back side 52 of the device there are electrodes A2, B2 aremounted for touching the chest of the patient conducting the recordingin the same manner as in the preferred embodiment. On the front side 62of the device there are three electrodes, an active electrode C2, areference electrode D2 and a ground electrode G2. All three electrodesC2, D2 and G2 have elongated, beam or band like shape and are integratedon the front side 62 of the device, preferably along the two longer,parallel edges of the housing 32 so as to be partially accessible fromthe sides. In the recording position, the electrodes C2, D2 and G2 aretouched by fingers of the left and right hand, in the manner equivalentto the one shown for electrodes C, D and G shown in FIG. 2A,respectively. This electrode arrangement is suitable if the device isrealized as a modified mobile phone that includes measuring electrodesand the cardiac signal recording module, or if it is realized as adevice that is attached to the mobile phone as a case or interchangeableback cover. In such embodiment, the elongated electrodes may be a partof the frame surrounding the display of the mobile phone or tablet.

Beside, this alternative electrode arrangement, featuring two electrodeson one side and on electrode on the opposite side, fulfills therequirement of asymmetry as well, needed for avoiding finger switching.

In another alternative embodiment, the device is a modified mobile phonethat includes recording electrodes and the cardiac signal recordingmodule, with a touch screen. The three hand electrodes for pressing withhands or fingers are realized as transparent conductive areasincorporated in a transparent layer covering the display of the phone,arranged in the same way as hand electrodes in the preferred embodiment.The smart phone application will mark the conductive areas on the screenwith a special color when the cardiac signal recording application isactive.

In another alternative embodiment, the device contains self-adhesivepatch with the chest electrodes. The self-adhesive patch is attached onthe user chest enabling the same chest electrode positions for thebaseline and all subsequent diagnostic recordings as described above.Alternatively or additionally, the apparatus (e.g., system) may includea patch having a docking region for connecting with any of theelectrode-including devices described herein, that may be used toconnect (or provide fiduciary reference for) the device to the samelocation on a user's chest. For example, a docking adhesive patch mayinclude a mating component or region that connects to the device to holdthe chest electrodes on the device in a reproducible location on theuser's chest. In some variations, the docking adhesive comprises aBand-Aid type material that is worn by the user over an extended periodof time (e.g., hours, days, weeks), and may be replaced with anotheradhesive to maintain the same reference location.

FIG. 7 shows another embodiment of the device realized as an extension83 to a mobile phone, such as a case or interchangeable back cover,having a form of a so called flip case or wallet for mobile phone,incorporating chest electrodes A3 and B3 on the back side of the device,and the left and right hand finger electrodes C3, D3 and G3 incorporatedin the flip-type phone display cover 93 of mobile phone casing.

FIG. 8 shows a block diagram of the method for automated detection ofAMI according to the preferred embodiment of the invention. A method forautomated detection of AMI (or ischemia) may include all or some of thesteps described below. First, placing the device in a recording positionon the user chest.

An optimal position of the handheld device on the chest is with centerof the device on the left side of the chest approximately above thecenter of the heart muscle. In this position, the chest electrodes areapproximately on the midclavicular line, the vertical line passingthrough the midpoint of the clavicle bone, same as for the V4 electrodeof the conventional ECG, and the lower chest electrode is at about thelevel of the lower end of the sternum. The user presses one activeelectrode and one ground electrodes with the fingers of the left handand one active electrode with the finger of the right hand on the frontside of the device.

The method may also include acquisition of a first 3 lead cardiacrecording and communicating the signals to the processing unit. The userof the automated AMI diagnostic system may perform the recording of the3-lead cardiac signal by holding the handheld device against the chestfor a short period of time (e.g., at least 30 seconds, at least 20seconds, at least 10 seconds, at least 5 seconds, etc.). The recordingis stored in the memory of the device and then transmitted to the remotePC computer via commercial communication network.

The method may also include storage of the first recording in the database of the processing unit as a baseline. After performing the firsttransmission of his/her cardiac signal, the cardiac signal recording isstored in a remote processor, and the user may be registered in thediagnostic system. Before this first transmission, the user or hisMD/nurse may enter (via a dedicated web site) his medical data such asage, gender, risk factors for cardiovascular disease, etc., and indicateif he/she is currently having chest pain or any other symptom suggestingischemia. If the answer is negative, this first cardiac recording iskept in the diagnostic system as a baseline recording that will serve asa reference for comparison in any further transmission when symptomssuggesting ischemia may occur.

The method may further include acquisition of the 3 lead cardiacdiagnostic recording and communicating the signal to the processingunit. Any subsequent recording after the baseline recording has beenaccepted and stored in the data base is considered to be diagnosticrecoding. The user of the automated AMI diagnostic system performs thediagnostic recording of the 3-lead cardiac signal by holding thehandheld device against the chest for at least 10 seconds. Thediagnostic recording is stored in the memory of the device and thentransmitted to the remote PC computer via commercial communicationnetwork.

In general, the methods described herein may include processing of thestored signals of baseline and diagnostic recordings by the processingunit. Processing may include pre-processing. For example theapparatus/method may be configured to let Va,Vb,Vc be the 3 specialleads recorded using the handheld device. Before performing anyanalysis, cardiac signal must be “cleaned” from the disturbing factorslike power line interference, baseline wandering and muscle noise. Whilethe former two may be removed using standard adaptive filtering andcubic spline techniques, respectively, the latter is suppressed usingtime-averaging median beat procedure.

To create a median beat, the entire cardiac signal may be delineated,resulting in set of fiducial points S={P₁, P₂, . . . , P_(n) }, wherePi={Q_(i), R_(i), J_(i), T_(i,end)} (or points equivalent to theselocations) are fiducial points of i-th beat. Based on S, the signal isthen divided into n individual beats of the same length. Finally,individual beats are synchronized using cross-correlation (CC) and foreach sample median value across all n beats is calculated. Thus, theentire cardiac signal is represented by the single most-representativemedian beat. A set of fiducial points P={Q, R, J, T, T_(end)} associatedto the median beat are simply calculated as median values of thefiducial point of the individual beats.

Techniques for obtaining representative beat other than median beat mayalso be used. The delineation of the cardiac signal resulting infiducial points for each beat may be done using different techniqueslike wavelet transform, support vector machine, etc.

The same pre-processing procedure is used for both baseline anddiagnostic recording.

If the lead recorded between the left and the right hand, or other leadcapturing the signal in the lateral direction, is inverted, the user isalerted to repeat the recording using the correct recording position.

The processing may also include beat alignment. For example, theapparatus or method may be configured to let B and D denote to themedian beats extracted from the baseline and diagnostic ECGs,respectively, and PB and PD are their associated fiducial points. Thegoal of beat alignment is to bring B and D in the same time frame so asthe corresponding points are accurately synchronized. This involvesfinding of such transformed B, referred to as B*, so that it isoptimally synchronized to the D. The applied transformation ispiece-wise uniform re-sampling of B, so that corresponding segments inB* and D, defined by PB and PD, respectively, have the same number ofsamples. Optimal alignment is obtained by searching for such fiducialpoints PB* that optimize cost function or similarity measure (SM) whichquantifies the alignment:

$\begin{matrix}{P_{B}^{*} = {\underset{P_{B}}{\arg{opt}}{SM}}} & (1)\end{matrix}$

B* is then obtained by transforming B using the P_(B)*.

In the present embodiment, we used CC which is commonly used SM forshape-based alignment problems. However, use of solely CC may lead towrong alignment as shape in B and D may be significantly different.Therefore, we introduce weighting functions f_(wi), which penalizeslarge deviations from the P_(B), as the fiducial points P_(B) areassumed to be accurately known:

$\begin{matrix}{f_{wi} = e^{- {(\frac{\Delta P_{Bi}}{ci})}^{2}}} & (2)\end{matrix}$

where i=Q, R, J, T, T_(end), ΔP_(Bi) is deviation from the i-th fiducialpoint and ci is scaling factor which depends on the fiducial points.Namely, as the R point is the most stable reference in ECG signal, itsdeviation is penalized the most. On the other hand, as J and T_(end)points are the least stable, thus, larger deviations are allowed. Theoverall SM is then calculated as product of CC and sum of weightingfunctions f_(wi):SM=CC(B(P _(B)),D)Σ_(i=1) ⁵ f _(wi)(|P _(B) −P _(Bi)|)   (3)

Finally, according to the Eq. (1) the B* is obtained by finding optimumof SM given in Eq. (3).

The processing may also include compensation for chest electrodemispositioning. During regular use of the handheld device, chestelectrodes may not be placed on the same spot every time, thus leadingto changes in shape of cardiac signal even in absence of any pathology.This change can be modeled as “virtual” heart electrical axis deviationin the Va,Vb,Vc leads vector space if lead positions are assumed to beconstant, with the heart electrical axis represented by the R vector—theheart vector at the moment of maximal magnitude in the QRS complex (orequivalent region in the three-lead cardiac signals described herein).However, this is undesired property as the difference signal ΔD will besignificant, even though there are no pathologically induced changes. Toovercome this problem, we transform D, resulting in D*=TD, so that itsheart electrical axis overlaps with the axis of B*. The transform T iscalculated using least squares method and Q-J segment (QRS complex) of Dand B* as input.

In general, processing may also include calculating difference signal,representing the change between baseline and diagnostic3 cardiac leadssignals. The difference signal ΔD* is calculated as:ΔD*=D*−B*   (4)

Ultimately, such difference signal ΔD* will reflect solelypathologically induced changes and it will be independent on heart axisdeviation.

Since the quality of the device misplacement compensation decreases withincrease of the angle heart axis deviation, if the angular change isgreater than a threshold, such as 15 deg, the user is prompted to choosea position that is closer to the baseline position.

The processing methods and apparatus described herein may also includedetection of ischemic changes. The STE is the most common ECG change incase of ischemia, measured usually at the J point or up to 80 mseclater. In the present solution, the ischemic changes are detected bycomparing the test recording to the baseline recording. In the preferredembodiment, the parameter or “marker” for ischemia detection is STVM (orequivalent region in the cardiac signals described herein), the vectormagnitude of the corrected difference signal AD^(*) at 80 msec after theJ point (J+80 msec), compared to a predefined threshold, such as 0.1 mV.

In other embodiments, vector magnitude in other time points may be usedas marker for ischemia, such as J point, J+60 msec, T max, etc. Othermarkers may be used that describe the shape of the ST segment (ECGsignal segment between J and J+80 msec points, or similar). Such amarker is the “Clew”, defined as the radius of the sphere whichenvelopes the vector signal hodograph between J and J+80 msec points.Also, other composite markers may be used, such as a logistic regressionusing a linear combination of STVM and Clew markers.

To compensate for signal shape change over time, a number of baselinerecordings, taken by the user over a period of time, may be used to forma reference that forms a 3D contour in the vector space defined by the 3special cardiac leads (instead of a single point when single baselinerecording is used). In using such a 3D contour reference, the ST vectordifference (STVD) will be defined as a distance from the 3D contourinstead from the baseline ST vector. If more than one parameter is usedfor ischemia detection, such a reference contour would be constructed asa hyper-surface in a multidimensional parameter space defined by suchparameters. In this case a hyper-distance from the referencehyper-surface will be defined in the said parameter space.

In users having cardiac condition with intermittent signal shapechanges, compensation for such changes may be done by forming two groupsof baseline recordings (at least two recordings) to define thereference, one with normal signals and one with the said condition.These two groups will form two 3D contours in the vector space, forminga reference for comparison, and the ST vector difference (STVD) will bedefined as a distance from closest point on the two 3D contours. If morethan one parameter is used for ischemia detection, such referencecontours would be constructed as two hyper-surfaces in amultidimensional parameter space defined by such parameters. In thiscase a hyper-distance from the reference hyper-surface will be definedin the said parameter space.

Any of these methods and apparatuses may be configured for communicatinginformation by the processing unit to the device. The created diagnosticinformation may be transmitted from the remote processor (e.g., a PCcomputer, server, etc.) to the device memory via commercialcommunication network. The method and apparatuses may also be configuredfor communicating the diagnostic information by the device to thepatient. The received diagnostic information may be presented to theuser in a form of characteristic sound, voice, graphics or text.

Additionally, an approximate conventional 12 lead ECG signal may be sentto the user's physician for evaluation. This signal may be produced asan approximate reconstruction of conventional 12 leads by transformingthe 3 special cardiac leads signals recorded by the user. Thisreconstruction may be obtained by multiplication of the 3 specialcardiac leads with a 12×3 matrix. In one embodiment, this matrix may beobtained computationally by using a general solution of potentialsdistribution on the surface of the human body, similar to thosepreviously described for defining a conventional vector cardiogram. Inanother embodiment, this matrix may be obtained as a population matrix,that is a matrix with coefficients that are calculated as an average, ormedian, values of individual matrices obtained by simultaneouslyrecording conventional 12 lead ECG and 3 special cardiac leads in apopulation of individuals, with each individual matrix obtained usingleast squares method. In yet another embodiment, multiple matrices maybe used in corresponding user groups defined by simple parameters of thebody shape and structure, like gender, height, weight, chestcircumference, etc., that may be easily obtained by the user. Also,matrix coefficients may be obtained as continuous functions of such bodyparameters.

EXAMPLES

A clinical study was done to evaluate the diagnostic accuracy of themethods described above for detecting myocardial ischemia provoked byballoon inflation in coronary arteries during a PCI (PercutaneousCoronary Intervention) procedure.

In this example, data was acquired continuously. Continuous data fromstandard 12 lead ECG with additional three special leads were obtainedfrom each patient during the entire period of balloon occlusion, and fora short period before and after. Target duration for balloon occlusionwas at least 90 sec if the patient is stable. In each patient, onebaseline recording was taken prior to the beginning of the PCIprocedure, and one pre-inflation during the procedure, prior to firstballoon insertion. In each lesion/intervention site, one inflationrecording was taken just before the balloon deflation. The analyzed dataset contains ECG recordings of 66 patients and 120 balloon occlusions(up to three arteries inflated per patient).

Data was analyzed by the methods described above (using the embodimentwith a linear combination of STVM and “Clew” markers), and results werecompared to the interpretation of the same data set by three experiencedcardiologist (one interventional cardiologist, two cardiacelectrophysiologists), blinded to any clinical data. All inflationrecordings were assumed to be ischemia-positive and all pre-inflationrecordings to be ischemia-negative. The study data set was divided intotwo sets of approximately same sizes, learning and test sets (using arandom number generator). The markers for ischemia detection were chosenand marker thresholds tuned on the learning set before the algorithm wasapplied to the test set.

Table 1, below illustrates the results of this study, comparingautomatically scored readings with readings scored by human (e.g.,cardiologist), showing a greater success rate using the automaticmethods described herein compared to those of trained human experts(human reader's average).

TABLE 1 Sensitivity, specificity and accuracy of the automated methodcompared to human expert reading. SEN [%] SPE [%] ACC [%] Automatedmethod 89.06 91.18 89.80 Human readers 76.11 64.14 71.86 Difference12.95 27.04 17.93

The results given in Table 1 show the superiority of using theavailability of the reference baseline cardiac recording fordistinguishing new from old ST deviation.

Another clinical study was done to evaluate the diagnostic accuracy ofthe algorithm based on 3 orthogonal cardiac leads in detecting AtrialFibrillation. The data set included 453 recordings from 25 patientsafter Pulmonary Vein Isolation (227 recordings with sinus rhythm and 226with Atrial Fibrillation). The “Clew” marker was applied to the P wave,combined with commonly used RR interval marker. Table 1, belowillustrates the results of this study.

TABLE 2 Performance of the automated method in detecting AtrialFibrillation SEN [%] SPE [%] ACC [%] Automated method 99.12 92.04 95.58

When a feature or element is herein referred to as being “on” anotherfeature or element, it can be directly on the other feature or elementor intervening features and/or elements may also be present. Incontrast, when a feature or element is referred to as being “directlyon” another feature or element, there are no intervening features orelements present. It will also be understood that, when a feature orelement is referred to as being “connected”, “attached” or “coupled” toanother feature or element, it can be directly connected, attached orcoupled to the other feature or element or intervening features orelements may be present. In contrast, when a feature or element isreferred to as being “directly connected”, “directly attached” or“directly coupled” to another feature or element, there are nointervening features or elements present. Although described or shownwith respect to one embodiment, the features and elements so describedor shown can apply to other embodiments. It will also be appreciated bythose of skill in the art that references to a structure or feature thatis disposed “adjacent” another feature may have portions that overlap orunderlie the adjacent feature.

Terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention.For example, as used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, steps, operations, elements, components, and/orgroups thereof. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items and may beabbreviated as “/”.

Spatially relative terms, such as “under”, “below”, “lower”, “over”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if a device in thefigures is inverted, elements described as “under” or “beneath” otherelements or features would then be oriented “over” the other elements orfeatures. Thus, the exemplary term “under” can encompass both anorientation of over and under. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. Similarly, the terms“upwardly”, “downwardly”, “vertical”, “horizontal” and the like are usedherein for the purpose of explanation only unless specifically indicatedotherwise.

Although the terms “first” and “second” may be used herein to describevarious features/elements (including steps), these features/elementsshould not be limited by these terms, unless the context indicatesotherwise. These terms may be used to distinguish one feature/elementfrom another feature/element. Thus, a first feature/element discussedbelow could be termed a second feature/element, and similarly, a secondfeature/element discussed below could be termed a first feature/elementwithout departing from the teachings of the present invention.

As used herein in the specification and claims, including as used in theexamples and unless otherwise expressly specified, all numbers may beread as if prefaced by the word “about” or “approximately,” even if theterm does not expressly appear. The phrase “about” or “approximately”may be used when describing magnitude and/or position to indicate thatthe value and/or position described is within a reasonable expectedrange of values and/or positions. For example, a numeric value may havea value that is +/−0.1% of the stated value (or range of values), +/−1%of the stated value (or range of values), +/−2% of the stated value (orrange of values), +/−5% of the stated value (or range of values), +/−10%of the stated value (or range of values), etc. Any numerical rangerecited herein is intended to include all sub-ranges subsumed therein.

Although various illustrative embodiments are described above, any of anumber of changes may be made to various embodiments without departingfrom the scope of the invention as described by the claims. For example,the order in which various described method steps are performed mayoften be changed in alternative embodiments, and in other alternativeembodiments one or more method steps may be skipped altogether. Optionalfeatures of various device and system embodiments may be included insome embodiments and not in others. Therefore, the foregoing descriptionis provided primarily for exemplary purposes and should not beinterpreted to limit the scope of the invention as it is set forth inthe claims.

The examples and illustrations included herein show, by way ofillustration and not of limitation, specific embodiments in which thesubject matter may be practiced. As mentioned, other embodiments may beutilized and derived there from, such that structural and logicalsubstitutions and changes may be made without departing from the scopeof this disclosure. Such embodiments of the inventive subject matter maybe referred to herein individually or collectively by the term“invention” merely for convenience and without intending to voluntarilylimit the scope of this application to any single invention or inventiveconcept, if more than one is, in fact, disclosed. Thus, althoughspecific embodiments have been illustrated and described herein, anyarrangement calculated to achieve the same purpose may be substitutedfor the specific embodiments shown. This disclosure is intended to coverany and all adaptations or variations of various embodiments.Combinations of the above embodiments, and other embodiments notspecifically described herein, will be apparent to those of skill in theart upon reviewing the above description.

What is claimed is:
 1. An apparatus configured to provide automatedcardiac diagnostics, the apparatus comprising: a housing comprising atleast four electrodes connected to a processor within the housing;wherein the processor is configured to: acquire a first set of at leastthree orthogonal leads from a patient's chest and hands at a first time;acquire a second set of at least three orthogonal leads from thepatient's chest and hands a second time; determine if the second set ofat least three orthogonal leads is rotated relative to the first set ofat least three orthogonal leads in a three-dimensional (3D) vector spaceand compensate for any rotation; perform a beat alignment on the firstand second sets of at least three orthogonal leads to synchronizerepresentative beats from the first and second sets of at least threeorthogonal leads; calculate a difference signal representing the changebetween the first and second at least three orthogonal leads; detect acardiac condition by one or both of: comparing parameters of the firstand second at least three orthogonal leads to one or more predefinedthresholds or by comparing parameters of the difference signal to apredefined threshold; and communicate the cardiac condition to thepatient.
 2. The apparatus of claim 1, wherein the housing has fourintegrated electrodes configured to be placed against the patient'schest.
 3. The apparatus of claim 1, wherein the processor is configuredto detect the cardiac condition comprising one or more of: acuteischemia, atrial fibrillation, atrial flutter, premature ventricularcontractions (PVCs), and premature atrial contractions (PACs).
 4. Theapparatus of claim 1, wherein the processor is further configured tocommunicate the cardiac condition to a remote processor.
 5. Theapparatus of claim 1, wherein the processor is configured to pre-processthe first and second sets of at least three orthogonal leads to achieveone or more of: eliminate power line interference, baseline wanderingand/or muscle noise; obtain a representative beat using fiducial pointsand median beat procedure; and check for switching of the left and rightfinger.
 6. The apparatus of claim 1, wherein the processor is configuredto detect the cardiac condition by determining the Clew of a P wave andprocessing said Clew in order to detect atrial fibrillation.
 7. Theapparatus of claim 1, wherein the processor is configured to present avisual and/or audible alert to the patient.
 8. The apparatus of claim 1,wherein the processor is further configured to calculate the differencesignal based on the synchronized representative beats from the first andsecond sets of at least three orthogonal leads.
 9. The apparatus ofclaim 1, wherein the processor is further configured to perform the beatalignment based on a piecewise resampling of one of the first and secondsets of at least three orthogonal leads.
 10. The apparatus of claim 9,wherein the piecewise resampling is based on fiducial points of thefirst and second sets of at least three orthogonal leads.
 11. Theapparatus of claim 1, wherein the processor is further configured tocompensate for electrode mispositioning between the first set of atleast three orthogonal leads and the second set of at least threeorthogonal leads.
 12. The apparatus of claim 11, wherein the processoris configured to determine a first vector associated with the first setof at least three orthogonal leads and a second vector associated withthe second set of at least three orthogonal leads.
 13. The apparatus ofclaim 12, wherein the first vector and the second vector are based on amaximal magnitude of a QRS complex in the first set of at least threeorthogonal leads and the second set of at least three orthogonal leads.14. The apparatus of claim 1, wherein the housing comprises two chestelectrodes and three non-chest electrodes.
 15. The apparatus of claim 1,wherein the 3D vector space is defined by the first set of at leastthree orthogonal leads.
 16. The apparatus of claim 1, wherein theprocessor is further configured to: calculate an angular change betweenthe first set of at least three orthogonal leads and the second set ofat least three orthogonal leads; and alert the patient to reposition thehousing based on the angular change greater than a threshold.
 17. Theapparatus of claim 1, wherein the first set of at least three orthogonalleads and the second set of at least three orthogonal leads are acquiredthrough the at least four electrodes.
 18. An apparatus configured toprovide automated cardiac diagnostics, the apparatus comprising: ahousing comprising at least four electrodes connected to a processorwithin the housing; wherein the processor is configured to: acquire afirst set of at least three orthogonal leads from a patient's chest andhands at a first time; acquire a second set of at least three orthogonalleads from the patient's chest and hands a second time; perform a beatalignment on the first and second sets of at least three orthogonalleads to synchronize representative beats from the first and second setsof at least three orthogonal leads, wherein beat alignment is based on apiecewise resampling of one of the first and second sets of at leastthree orthogonal leads; calculate a difference signal representing thechange between the first and second at least three orthogonal leads;detect a cardiac condition by one or both of: comparing parameters ofthe first and second at least three orthogonal leads to one or morepredefined thresholds or by comparing parameters of the differencesignal to a predefined threshold; and communicate the cardiac conditionto the patient.
 19. An apparatus configured to provide automated cardiacdiagnostics, the apparatus comprising: a housing comprising at leastfour electrodes connected to a processor within the housing; wherein theprocessor is configured to: acquire a first set of at least threeorthogonal leads from a patient's chest and hands at a first time;acquire a second set of at least three orthogonal leads from thepatient's chest and hands a second time; compensate for electrodemispositioning between the first set of at least three orthogonal leadsand the second set of at least three orthogonal leads; perform a beatalignment on the first and second sets of at least three orthogonalleads to synchronize representative beats from the first and second setsof at least three orthogonal leads; calculate a difference signalrepresenting the change between the first and second at least threeorthogonal leads; detect a cardiac condition by one or both of:comparing parameters of the first and second at least three orthogonalleads to one or more predefined thresholds or by comparing parameters ofthe difference signal to a predefined threshold; and communicate thecardiac condition to the patient.
 20. An apparatus configured to provideautomated cardiac diagnostics, the apparatus comprising: a housingcomprising at least two chest electrodes and three non-chest electrodesconnected to a processor within the housing; wherein the processor isconfigured to: acquire a first set of at least three orthogonal leadsfrom a patient's chest and hands at a first time; acquire a second setof at least three orthogonal leads from the patient's chest and hands asecond time; perform a beat alignment on the first and second sets of atleast three orthogonal leads to synchronize representative beats fromthe first and second sets of at least three orthogonal leads; calculatea difference signal representing the change between the first and secondat least three orthogonal leads; detect a cardiac condition by one orboth of: comparing parameters of the first and second at least threeorthogonal leads to one or more predefined thresholds or by comparingparameters of the difference signal to a predefined threshold; andcommunicate the cardiac condition to the patient.
 21. An apparatusconfigured to provide automated cardiac diagnostics, the apparatuscomprising: a housing comprising at least four electrodes connected to aprocessor within the housing; wherein the processor is configured to:acquire a first set of at least three orthogonal leads from a patient'schest and hands at a first time; acquire a second set of at least threeorthogonal leads from the patient's chest and hands a second time;calculate an angular change between the first set of at least threeorthogonal leads and the second set of at least three orthogonal leadsand alert the patient to reposition the housing based on the angularchange greater than a threshold; perform a beat alignment on the firstand second sets of at least three orthogonal leads to synchronizerepresentative beats from the first and second sets of at least threeorthogonal leads; calculate a difference signal representing the changebetween the first and second at least three orthogonal leads; detect acardiac condition by one or both of: comparing parameters of the firstand second at least three orthogonal leads to one or more predefinedthresholds or by comparing parameters of the difference signal to apredefined threshold; and communicate the cardiac condition to thepatient.